The use of the so‐called ‘superchilling’ technique for the transport of fresh fishery products

Abstract

Superchilling entails lowering the fish temperature to between the initial freezing point of the fish and about 1–2°C lower. The temperature of superchilled fresh fishery products ( SFFP ) in boxes without ice was compared to that of products subject to the currently authorised practice in boxes with ice ( CFFP ) under the same conditions of on‐land storage and/or transport. A heat transfer model was developed and made available as a tool to identify under which initial configurations of SFFP the fish temperature, at any time of storage/transport, is lower or equal to CFFP . A minimum degree of superchilling, corresponding to an ice fraction in the fish matrix of SFFP equal or higher than the proportion of ice added per mass of fish in CFFP , will ensure with 99–100% certainty (almost certain) that the fish temperature of SFFP and the consequent increase of relevant hazards will be lower or equal to that of CFFP . In practice, the degree of superchilling can be estimated using the fish temperature after superchilling and its initial freezing point, which are subject to uncertainties. The tool can be used as part of ‘safety‐by‐design’ approach, with the reliability of its outcome being dependent on the accuracy of the input data. An evaluation of methods capable of detecting whether a previously frozen fish is commercially presented as ‘superchilled’ was carried out based on, amongst others, their applicability for different fish species, ability to differentiate fresh fish from fish frozen at different temperatures, use as a stand‐alone method, ease of use and classification performance. The methods that were considered ‘fit for purpose’ are Hydroxyacyl‐coenzyme A dehydrogenase ( HADH ) test, α‐glucosidase test, histology, ultraviolet–visible–near–infrared ( UV ‐ VIS / NIR ) spectroscopy and hyperspectral imaging. These methods would benefit from standardisation, including the establishment of threshold values or classification algorithms to provide a practical routine test.

Effects of Modified Atmosphere Packaging with Different Gas Ratios on the Quality Changes of Golden Pompano (Trachinotus ovatus) Fillets during Superchilling Storage

“…Liu et al [7] also found that superchilling storage can inhibit the growth of microorganisms and retard the hydrolysis of proteins more effectively than at 0 • C in grass carp fillets. Superchilling preservation technology has many advantages in preserving food, but the temperature fluctuation, repeated freezing and thawing caused by the instrumentation or external environment can have adverse effects on the protein quality of the product [8,9]. Therefore, it is necessary to combine other preservation technologies to meet the market requirements for the freshness of aquatic products.…”

Guidance on protocol development for EFSA generic scientific assessments

“…Here temperature and growth have been modelled. Superchilling opinion (EFSA BIOHAZ Panel, 2021 ): https://www.efsa.europa.eu/en/efsajournal/pub/6378 . Here only temperature was modelled; no need for modelling the growth of pathogens.…”

Extending the Shelf Life of Atlantic Salmon (Salmo salar) with Sub-Chilled Storage and Modified Atmosphere Packaging in Recyclable Mono-Material Trays

“…Super-chilling is a food conservation method that lowers the product’s internal temperature to below 0 °C between conventional chilling and freezing [ 9 ]. The term “super-chilling” has been interchangeably used with terms like “supercooling”, “sub-chilling”, “deep chilling”, “ultra-chilling”, “surface freezing”, and “partial freezing” [ 10 , 11 ]. This definition is currently not explicitly defined in the legislation [ 11 ], although several studies define super-chilling as lowering the internal temperature 1–2 °C below the freezing point of the product, with a certain degree of ice crystal formation [ 11 , 12 , 13 , 14 ].…”

“…The term “super-chilling” has been interchangeably used with terms like “supercooling”, “sub-chilling”, “deep chilling”, “ultra-chilling”, “surface freezing”, and “partial freezing” [ 10 , 11 ]. This definition is currently not explicitly defined in the legislation [ 11 ], although several studies define super-chilling as lowering the internal temperature 1–2 °C below the freezing point of the product, with a certain degree of ice crystal formation [ 11 , 12 , 13 , 14 ]. In this study, our focus is to lower the product’s internal temperature to that below melting ice down to the initial freezing point, with no formation of ice crystals.…”